If all your datasets have a common key, and you are just plotting different variables on multiple charts, you could try the most straightforward approach:
- Use a Join recipe to Join all your datasets at once on that common key
- Open the resulting dataset and head to the Charts tab. You will find that charts have a "Filter" box in their options, letting you filter your data.
- Create as many charts as you need. Of course you can publish any of these on the dashboard.
However, I am not sure that I understand correctly what you are trying to achieve. If the approach I pointed out is not possible and you need more flexibility, you could create a SQL Query dataset, and edit it until you found what you are looking for. Then if you want to keep it, create a SQL Query recipe, in order to save the results. The steps would look like this:
- Create a new dataset on your SQL database (it will appear in your flow as a single dataset, blue square). At creation screen, select Mode: "SQL query" and type a query
- On the dataset, create a chart. If you are not satisfied, go to settings tab, edit the query, and update charts.
- Once satisfied, copy the query to a SQL Query recipe (this one will appear in the flow as a code recipe, orange circle, outputting a dataset), this will create a managed dataset on which you can recreate a chart, and publish it.
- Rinse and repeat
Please don't hesitate to comment on that answer if you need clarification or if I missed something in your question!